1. Field of the Invention
The present invention relates to a technique capable of attaining a high-quality printing of characters by using a printing apparatus.
2. Description of the Related Art
At present, high-quality copy images can be easily obtained by using a color copier. Such a color copier is substantially constituted with a scanner unit for reading an image and a printing unit for printing a copy image. On outputting the copy image, light is first shed to a manuscript image on the scanner unit to read light reflected from the manuscript image, thereby creating image data. Then, the thus read image data is converted to data on ink amount of CYMK respective colors (color conversion processing) and printing is executed on the basis of the thus obtained data on ink amounts by the printing unit to output a high-quality copy image.
On the other hand, color copiers have a tendency that characters on an image will inevitably result in a reduction in quality. Specifically, where characters are read by using a scanner unit, even a black-color character reflects light to some extent and develops into a character having a tinge of gray due to the thus read image data. Then, when the gray-tinged character is converted to data on ink amounts, it is converted to data on ink amounts in which CMY respective color inks are used in addition to K (black) ink for expressing gray color. Thus, the inks are used in an increased amount in printing and ooze out. Due to the above reason and others, characters undergo reduction in quality such as blurred outlines of the characters. Thus, there has been proposed a technique in which a character-specific color conversion table which is used for conversion to data on exclusive amounts of K ink is provided in addition to an ordinary color conversion table, and the character-specific color conversion table is used at a part of characters to effect conversion to the data on exclusive amounts of K ink, thereby avoiding characters blurred with inks or others to attain a high-quality printing of characters, as disclosed in JP-A-2006-197549.
However, the above-proposed a technique has a problem that a high-quality copy image is not easily obtained. Specifically, it is necessary to execute color conversion processing, while the ordinary color conversion table is switched to the character-specific color conversion table or vice versa, thereby the color conversion processing is inevitably complicated. For this reason, such a problem is posed that a high-quality copy image is not output easily.